Fluid-pressure brake apparatus for railway vehicles



May 28, 1929. 1,714,669.

FLUID PRESSURE BRAKE APmRA'rus FOR-RAILWAY VEHICLES w. HILDEBRAND Filed March 1928 Patented May 28, 1929,

matte VJILHELM HILDEBRAND, OF LICHTERFELDE, BERLIN, GERMANY.

FLUID-PRESSURE BRAKE APPARAT'US FOR RAILWAY VEHICLES. 7

Application filedMarch 8, 1928, Serial No.

This invention relates to" fluid pressure brake apparatus for railway vehicles, of the kind described in the specification of my prior Patent No. 1,618,197, in which at the beginning of an application of the brake a transfer chamber was arranged to draw off from the train pipe a quantity of compressed air corresponding with the quantity displaced by the stroke of the control piston of the brake device, and thus to prevent the air thus displaced from affecting the quick trans mission of the fall of pressure in the train pipe. The inlet of this transfer chamber was controlled by a separate accelerator piston, and its outlet, which was throttled, was controlled by the control slide of the main brake piston. A certain additional load on the brake device was involved by the use of a separate piston and valve for controlling the inlet of the transfer chamber, and the avoidance of such additional load is an object of the present invention, according to which the brake mechanism is simplified by allotting the control of the inlet of the transfer chamber to the main piston of the brake control valve, the constructional arrangements forexercising this control being such that immediately on the inception of the braking action the transfer chamber is connected with the train pipe, before its outlet is closed, the throttling of the said outlet preventing eX- cessive loss of air from the transfer chamber until the outlet is closed by the main slide valve. Other objects and advantages of the invention will appear from the following description read in conjunction with the accompanying diagrams exemplifying two ways of putting the invention in practice.

Figure 1 represents diagrammatically the parts of an air brake to which the present invention relates, in the release position.

Figure Qrepresents the same parts in the position of application of the brake.

Figure 3 represents a modified construction wherein a separate slide valve controls the inlet of the transfer chamber.

The reference letter a indicates the graduating slide valve, 7) the main slide valve, 0 the slide face, Zthe port of the slide face connected to the train pipe, at the port leading to the transfer chamber, 0 the port leading into the atmosphere, in which port 0 is inserted a disc cl provided with a throttle openeeaose, and in Germany January 19, 1928.

m of the main slide valve 6.

rVhen the braking action is started, immediately at the beginning of the movement of the graduating valve a, the port Z, of the main slide valve, coinciding with the port Z in the slide face, will be connected to the port u of the main slide valve, and therefore the train pipe and transfer chamber will be con nected through the port a, so that an additional fall of pressure, corresponding to the volume of the transfer chamber and to the stroke volume of the control piston, will at once take place in the main pipe, owing to which the further movement of the control piston will be assisted. The outlet 0 of the transfer chamber, which still remains open during the movement of the graduating slide valve, will be at once closed when the main slide valve 6 begins to move, whilst the connection between the port Z leading to the train pipe, and the port a leading to the transfer chamber, remains in existence through the passages Z,w/-u, as the port Z remains over the extension of the upper orifice of the port Z, extending in the direction towardsthe control piston, see Figure 2. w

In the constructional form of the invention according to Figure 3 the inlet opening a of the transfer chamber U is controlled by a small slide valve a, which covers the duct 10 l with a very slight lap and which is moved by the controlling piston conjointly with the normal graduating slide valve a. The outlet from the transmission chamber is effected through the throttling device d and through the main slide valve 6 and the opening 0 leading into the open air, when the main. slide valve is in the position of release.

It will be seen that in both the embodiments of the invention illustrated, the chamber inlet is immediately opened at the beginning,

the chamber outlet, the said outlet is entirely closed as soon as the movement of the main slide valve takes place, that is, immediately after the clearance or play between the graduating slide valve and the main slide valve has been taken up in the continued movement of the piston. 7

What I claim and desire to secure by Letters Patent of the United States is 1. In fluid pressure brake apparatus for railway vehicles, a control piston, a transfer chamber having an inlet and having also a throttled outlet normally open to the atmosphere, a valve movable by said piston and normally closing said inlet, said valve being adapted to open said inlet at the beginning of the operative stroke of said piston, a second valve also movable by said piston and so positioned in relation to the stroke of said piston as to close said outlet at a later period of said stroke. 7

2. In fluid pressure brake apparatus for railway vehicles, a control piston, a main slide Valve operable by said piston, a graduating slide valve also operable by said piston and movable to a predetermined extent in relation to sa1d main slide valve, a transfer chamber having an outlet normally open to the atmos- VILHELM HILDEBRAND. 

